how to bend a revolver mainspring?
 

I would like to know how to bend a stock S&W revolver mainspring to get a lighter trigger pull. I know that I can just buy reduced power Wolf springs and have bought them in the past. But having put Wolf springs in a bunch of guns, I now have a bunch of stock mainsprings and I’d like to see what I can do with them.

A gunsmith once did this for me and the result was pretty good, not quite as smooth or light as a Wolf, but noticeably better than before. Also, this bent spring gave me a trigger pull that was a bit heavier than a Wolf spring and worked with primers that were too hard for that particular gun using a Wolf reduced power mainspring.

I got a nylon wedge from Brownells (that they advertise for this purpose) but I don't know how to use it.

Thanks for any advice you all can provide!

You need to do what's called a "mandrel" bend which just means bend it over a curved form so you don't put a corner in it. I get three screwdrivers with round plastic handles (maybe 1 1/4" diameter) and set them up so the bend is centered about 2/3 of the way up from the bottom tip of the spring. Two screwdrivers on one side, one on the other so you are bending across the single one.

Before you start, lay the spring sideways and ink a line showing the starting curve so you can compare it after you bend it. To reduce strength, bend a little more curve into it. To make it stronger, you flatten it some.

Thanks bountyhunter. I will try it.

I like to bend mine similar to the Wilson or Miculek reduced springs and use a simple jig made of 2 nails set into a 2x4. Use one small nail that will engage the hooks and add another larger nail about an inch away to use as the bending point. Easy to control and repeatable.

Thanks Imashooter. Does anyone use the nylon wedge from Brownells? I'm curious because now that I've got it, I might as well use it.

Maybe you could post the part number, I never heard of it.

"Nylon wedge" is the name and 080-722-100 is the part number. Thanks for taking the time to give this some thought.

I can't see how that could be used except to wedge in between the frame and the spring to try and bend it while still installed in the gun...

I can't picture someone actually doing that, but I can't see any other way to use it.

I don't think I would use that.

springs
 

Jeff

Don't bend springs, or cut coils from trigger rebound springs all that is bad bad bad:(


If you must, and have to have a lighter spring(God knows why) pick a Wolf spring and install it, I have seen too many shooters turn there revolvers into junk real fast, improper bending will change smooth action into ****. Also add unnecessary stress to adjoining parts, remember the trigger pull is a long cycle all the parts depend on one another for fit and proper spring tension,

The short answer install a Wolf Type II is reduced power, Type one is factory power. They have a bend in the proper area and the right temper.

Old thread I know. However, I wanted to say that S&W bends the Wolff mainspring when adjust trigger pull to 10 lbs on their PC guns. Bend in the middle, no kinks, and measure pull weight. Adjust as needed.

I personally like the Wolff Reduced power spring and a socket set screw with the proper loc-tite. I think Tomcatt51 turned me on to that.

The Nylon wedge you are referring to is used as a take down tool to disconnect the mainspring from the hammer without unscrewing the mainspring strain screw. In the S&W armorers kit it is a wooden wedge. Brownells made it of nylon for it's longer lasting properties over wood.

I just checked the Brownells site, ans they indicate that it can be used to re-arch the Mainspring. They have a live chat feature on the website, you,could ask,them about it. I've never seen one of those, so I can't offer any advce.

The primary purpose of the wedge is to be used to straighten cylinder yokes that are sprung.

If the cylinder is sprung upward, the wedge is pushed in between the frame and the closed cylinder, then tapped to bend the yoke.

I strongly suspect that if you try to bend the spring in the frame, what will happen is that you'll break the "fingers" on the spring or break the hammer stirrup the spring connects to before you get a bend in the spring.

These days with so many after market springs available, it's not really necessary to bend springs.
Instead you can install a after market spring and tune the spring tension screw to get whatever you want.

Yrs ago, I send my 29-2 to 300 gunsmith services in Colorado for an action job. It came back sweet. They bent the mainspring just below the hooks. At the time, it was a normal procedure that required taking the temper out of the spring, bend it, and re temper the spring. I just buy another Wolfe spring these days.

Charlie

A little off topic as to bending the spring but does lighten the spring. I'm not recommending or advocating doing it but I've seen it done. By lightly grinding on a belt sander, going slow not to overheat but to narrow the spring width. I guess maybe the same thing might be achieved by thinning the spring thickness rather than the width but I've not seen that done. I'm not an expert so regardless, I think bending would be better and with the availability of relatively inexpensive springs, a replacement would probably be better still.

If you get all rounds to fire and your double action pull is smooth between 8 and 9 lbs leave it alone.

If you must play with your action then back out the stain screw a 1/4 turn at a time till you no longer get good primer hits with all rounds firing.Then back it in 1 full turn.

I've done the Wolff Spring thing on a few Smith revolver and always go back to the factory springs and full strain on the mainspring.

First and foremost the revolver must be able to fire all rounds consistently.Anything less is a fail.

I would NOT bend a Smith Main Spring - but that's just my opinion. I have removed minor amounts from Strain Screws to lessen the pressure on the Main Spring and if necessary (although I have never needed to do this) a lighter one can be substituted in the originals place.

The only springs that I do bend for adjustments are the three finger springs in 1911's. Other than that, I do not bend them.

I don't care what named gunsmith or manufacturer 'bends' mainsprings while 'doing' a trigger job. It is a bad metallurgy practice and can lead to real problems. If your gun is a paper puncher, do anything you want. If it has any chance of being needed for self defense purposes.....leave the mainspring alone or buy an after market quality spring like produced by Wolff......

This is an interesting old thread, I am happy it was resurrected.

I have a 1st Gen Colt SAA circa 1904 that has been changed to a .38 Special with 2nd Gen parts. It's been fired a lot - so much so that the cylinder ratchet has peened the recoil shield. It's got about the smoothest and lightest cocking I've ever felt on a SAA.

Part of that is from use, but it also has a mainspring that has been worked on. It looks like someone used a flat file to round off the back side of the mainspring so that it is a convex arch from side to side. The spring looks very old and I know I've shot it plenty of times with no issues.

The gun is 100% reliable and I've never had light primer strikes. It makes me wonder if a S&W mainspring can be modified the same way.

Buy the Jerry K. shop manual for S&W revolvers.

I am sure it will tell you proper ways to reduce trigger pull.

In my experience, S&W has always had a decent SA pull, meaning quite light compared to others.

For my 629-2E, the SA pull was excellent, but the DA pull was horrendous and probably 15lbs+ if I could accurately measure it.

I installed an 11lb rebound spring, then modified and adjusted the tension screw on the mainspring until it would successfully rebound the trigger.

The SA is about 2.5lbs and the DA is about 9lbs now. Very smooth.

I'm with the buy Wolff springs camp if you want to tinker with springs, but there are many ways up the mountain to also include bending and grinding them, and shaving down the strain screw.

One note of caution in doing anything to the older S&W mainsprings, say, prior to 2000 or so; I've found that current factory mainsprings are thicker compared to the old days, and the result is a heavier and sometimes hitchier action. They're not making the old mainsprings anymore and I'd leave them be.

For many years people filed or ground mainsprings to lighten the tension even though experts said not to do it because the spring would sooner or later snap.
They did it anyway and were often shocked when the spring snapped soon after.

What happens is, the filing or grinding leaves scratches, often microscopic and those cause stress risers in the structure of the spring. That causes the spring to snap.
People were warned that any filing or grinding required extensive smoothing of the spring to remove even scratches that couldn't be seen to eliminate the stress risers, but even then the springs still tend to snap.

Again, with all the different types and brands of S&W mainsprings available, bending or grinding of springs is a relic of a different era before after market springs were available.

Layers and layers of mis-information here. Anyway you can't even work a Colt without knowing how to tweak and improve factory springs. Long before Wolf and the aftermarket parts business came on the scene S&W revolversmiths learned how to shape and tune main springs and it ain't done with heat, a wedge or screwdriver handles etc. The image shows stock factory far right, Wolf and two of my tuned K & L springs for comp guns. After 20-30K rounds they are still reliable enough to leave the strain screw setting depth as is. Enough said


Attachment 240234

Let me preface this by saying I have tried non of the solutions. On the other hand, for reasons having nothing to do with guns, I have studied about springs probably more than was good for me.

The strength of a flat spring is directly proportion to its width. Narrow it by 50% and cut its strength in half. Thickness is a much more complicated process. The relationship is "non linear". Calculating the strength reduction from a little thinning will be difficult. Bending changes a spring's "pre load" and also it's geometry, so the result will be trial error. Given those choices I'm pretty sure I'd grind a little off the sides.

Ed

garbler, so how did you bend them?

Stu

Instead of bending, grind a bit off of the width of the spring along the lower half of each side of it. Never take any metal off lower than the strain screw. Do it gradually in increments and reassemble. If you mess one up......they're cheap.
This has worked well for me.

I narrow Wolff Reduced Power springs occasionally but I remove material from the top half. It allows me to lighten the spring while controlling the installed arch of the spring and I want the additional arch in the top half.

I have nothing against bending them I just don't seem to have the knack.

You people are always looking for a quick fix or easy way that can be bought from Potterfield, Miculek or Utube. Your suspicious of gunsmiths and their charges since you can buy a video and some wonder parts and have an action job. Tell me how do you think Jerry Miculek learned any of his craft ? From his father-in-law of course who was a master gunsmith.

By thinking you can do a gunsmith's job in your rec room from a video is unfortunately the saddest of all statements on the future of real craftsmanship. I mean why even dedicate the years the money and time learning a trade when many out there think it's a gimmick and worth less than their yard maintenance crew charges. Well bending and tuning main springs or any flat spring is a gimmick ? So it should be easy to replicate. I guess in the final analysis there probably isn't one in fifty on this site who would know a real action job from a lighter trigger to save their lives.

garber, if that was an answer to my question about how you bend the springs, it was a pretty sad answer. You have no idea of who I am or what I am about. It was an honest question and it was not looking for a lecture in return.

Stu

I did a "narrowing" job on a stock SW mainspring mostly for curiosity to see how much it takes to get the strength down to about where a typical "reduced power" spring is..... and it took a lot of grinding. It was removing more metal than I would and still feel confident about the spring's integrity.

As for bending: you don't have to bend them much and if you spread it over a little distance (and use a curved piece to bend it on), the spring has no problem. I have done it on at least a dozen of my own smiths and never seen a spring fail or even "walk" to where it needed to be retensioned.

As for grinding strain screw ends..... hate that because it's non reversible and you need a micrometer to know what the thing is cut down to.

I like the Wolff ribbed springs for function but the groove in the spring tapers the end of the strain screw effectively shortening it by tapering tip of the screw. Pain in the rear to have to keep replacing the screw to maintain spring tension.

Speaking for the fifty, the only reason I started gunsmithing about 25 years ago was because I wanted trigger work done on my Beretta and the soonest I could get any smith to even look at it was about six months.

The problem is the kind of attitude I see shining through your post is pretty much what I have seen from a lot of smiths. Nobody here (except maybe you) is talking about a master gunsmith. But some of us have learned how to do some basic and very useful things to guns (at least, the brands I own) and we share it when somebody asks. Knowledge is power and not being able to do basic repairs or mods leaves a person at the mercy of gougers. Not all smiths gouge, but some do. My main gripe is the horrible service and ridiculous lead times (paging Doctor C+S....).

It's kind of ridiculous to take such offense when what we are talking about is tweaking a cheap spring. Worst he could do is mess up the spring and have to buy a new one for five bucks.

I agree 100%

This is an interesting thread on springs.

I think I will order a Wolff spring kit,,, and give it a go and see what happens.
(My self defense gun is an unmodified 629,, we are NOT discussing that one!!)

I would love to evaluate what a new, factory S&W mainspring is like.
Where can I order a new, S&W mainspring,,, ?

S&W and Brownells should have the factory springs and Brownells the Wolff along with other reduced power versions. I'm sure other places should have them too.

So true!
I don't try to do a master gunsmith trigger job but just doing the easy steps of putting in an 11lb. trigger rebound spring, decreasing the width of the mainspring or putting in a lighter mainspring on a J frame, stoning the bottom and side of the trigger rebound spring housing and the frame where it contacts with a small whetstone makes a world of difference.

Let's remember the question here was about modifying a mainspring. It wasn't about performing an action job, just modifying a factory spring. That's no big deal, and doesn't take rocket science or a degree in physics. I will say however that heating a spring for any purpose is a bad idea unless you understand a lot about metallurgy. Spring properties are made by heating to a certain temp, for a certain period of time, and using a certain type of quench. Miss any of these three important factors and the spring can either be too soft and just bend under pressure, or too brittle and break under pressure.

Now, on to the unasked, yet answered (?) question of action jobs and gunsmithing in general. A real gunsmith must be trained to work on all aspects of a firearm, from inspecting Damascus steel to fitting a Perrazi shotgun. However these people are few and far between. Just like the medical field has specialists, so does the gunsmithing field. For example, there are those who work on nothing but 1911's, and just like the medical field, these are the people you want working on your specific need. Doing a trigger job on a S&W isn't difficult, provided you are mechanically inclined and can read and more importantly follow instructions. I've worked on the actions of many 1911's and S&W revolvers. And although it was always this way, I'd now put my work up against anyone's. In fact paying a gunsmith for a trigger job was what started me doing my own when I completely dissatisfied with the quality of his work. But again, I posses the three traits I mentioned above, and never hesitated to shell out the bucks for specialized tools when needed. I liken doing an action job to replacing the brakes on a car. Any one with the traits mentioned above, and of course the proper tools, can do it, and for a lot less than the "professional" will charge. That in no way is meant to lessen the job done by a gunsmith (or an auto mechanic for that matter). I'm merely stating that doing an action job isn't magic, voodoo or some mystic ritual that only certain high priests can perform. If, however, you lack in the three areas I mentioned or don't have the proper tools, then I strongly urge you to have a professional do the work, whether it's an action job or a brake job on your car. Botched results can have similar ends. :eek:

And no, I won't work on your gun because I no longer have a license and consider myself retired. :p :D

I see that others have already given stern warnings. I am not trying to ruin your day or to be rude, but I will add my advice.

First, if you have to ask, you are not qualified to do a proper action job, which involves smoothing more than lightening. That out of the way, here is what you need to know, direct from a reputable manual on do-it-yourself gunsmithing of the S&W revolver:

"To bend mainspring to obtain lighter, reliable trigger pull weight:

Step 1: Remove and keep all parts of your revolver stock, and modify only replacement parts. You will need all of your original parts later. See step 4.
Step 2: Buy several replacement mainsprings.
Step 3: Prepare yourself for how unhappy you will be when you turn a perfectly reliable revolver into a piece of junk that will not reliably fire a cartridge.
Step 4: Use all of the original parts saved from Step 1 to restore your revolver to stock condition, and hope it works after your "kitchen table gunsmith job."

:)

Post #2 is your answer!

Works well, but you will have to play with the amount of arch you put in to get what you want.

Remember this is all done at room temperature, no heat involved at all.

I did a 586-8 with this Wolf kit:

171212
S&W - K,L,N FRAME RP SHOOTERS PAK TYPE 2

But it gave me a DA of less than 6lbs and I had 10% failure to fire due to light prime strikes. I used the middle rebound spring.
SA was 3.5-4LBs,

I took 30% of the arch out and got 8lbs DA pull and so far all is good.

If you run into hard primers then you might have issues.

I didn't read any of the posts following this one. Here's how to do it:

Don't . . .

Whenever I see that with a Wolff RP mainspring it was because the strain screw was short.... either intentionally as part of somebody's trigger job or the tip "angled off" over time.

Nope it is a new gun bought in Feb this year.
But that 14.5lb DA and 8lb SA was a killer on the arthritis in my knuckles.

That can happen. Sometimes you need a slightly longer strain screw with the Wolff Reduced Power Mainspring. A socket set screw works well but that is also on many of the purists "YOU CAN'T DO THAT!!!" list. A socket set screw (grade 8) is a much better piece than the S&W stainless strain screws which are a too soft material / heat treat.

S&W has been using the Wolff Reduced Power Mainspring in their PC guns for years (they're listed with a S&W part # in my 2006 S&W parts catalog) along with a longer strain screw.

As to bending springs, this is being blown out of all sense of proportion. These aren't highly stressed springs being worked near their design limits.

It never crossed my mind to use a set screw for this. I will do that for my partner if he likes what I have done.
Thanks for the tip.

I doubt we will shoot enough or live long enough to wear out these springs bent or not. I have cold bent leaf springs in punch presses for years to tune them up and seen 10,000,000 cycles on them doing just fine.

Jerry made a video on lightning trigger pull. I have it.